The memory capacity of a HDD (Hard Disk Drive) used as a recording apparatus for not only computers but also digital home appliances and portable music terminals is increasing rapidly. To increase the memory capacity, recording medium technology, control motor technology and magnetic head technology assume great roles. Out of these, the development of a magnetic head or a slider which floats at a height of several nm to read information recorded on a recording medium is important. To increase the memory capacity, the development of a thin magnetic head is now under way to further reduce the amount of floatation, that is, the distance between a recording medium and a thin film type magnetic head and the thickness of the thin film.
In general, this magnetic head is manufactured by forming and patterning a protective/insulating layer made of Al2O3 and a magnetic metal film made of Fe—Ni or Fe—Al—Si on a high-hardness ceramic substrate made of Al2O3—TiC, cutting and polishing them, forming a protective coat and surface finishing it. An air bearing surface, that is, a data read and write surface which floats by an air flow generated by the revolution of a recording medium, has been polished by using floating abrasive grain slurry. However, materials constituting the above magnetic head differ from one another in polishing ease, the smoothness of the floating surface of the magnetic head does not become satisfactory with a method using the floating abrasive grain slurry, the magnetic metal film which is a soft material is selectively polished, and the distance between the recoding medium and the magnetic metal surface becomes substantially long. The floating distance is becoming shorter due to a recent increase in memory capacity, and an increase in the distance by the selective polishing cannot be ignored.
Further, a scratch which is formed across the polished surface by the floating abrasive grains causes an electric short-circuit and deteriorates the characteristic properties of the magnetic head.
Then, to avoid this problem, there is proposed a method in which, after the air floating surface is polished with floating abrasive grain slurry, precision final polishing is carried out with lapping oil containing no floating abrasive grains (refer to JP-A 62-292358, JP-A 3-92264, JP-A 7-299737, JP-A 9-245333 and JP-A 2004-58220).
In the above method, after rough polishing is carried out with free abrasive grain slurry, final polishing is carried out by using lapping oil containing no abrasive grains to remove free abrasive grains which cause scratching or selective polishing so as to polish only with abrasive grains fixed on a plate, thereby obtaining a high-quality polished surface.
Meanwhile, due to a reduction in the thickness of an electric shield gap and use of a GMR (Giant Magneto-Resistive) head having a magnetically complex structure along with a rapid increase in the surface recording density of HDD, the damage of a magnetic head by ESD (Electrostatic Discharge) in the process of manufacturing the magnetic head is becoming a more and more serious problem. Since the damage of the magnetic head by ESD causes problems such as reductions in yield and the reliability of HDD, ESD countermeasures for the magnetic head are very important (refer to “ESD phenomenon in a HDD manufacturing process using a GMR head” written by Yoshiaki Mizoo, et al., [online], International Disk Drive Equipment Materials Association Japan, IDEMA Japan News No. 55, Jul. and Aug. editions of 2003).
In the conventional method in which polishing is carried out by using abrasive grains fixed on a platen and supplying a lubricating oil containing no abrasive grains, a lubricating oil containing a hydrocarbon solvent such as n-paraffin, isoparaffin or naphthene and additives has been used (refer to JP-A 2004-58220). However, the lubricating oil is insulating and has a problem that the magnetic head is destructed or the reliability of the magnetic head is reduced by accumulated static charge during polishing. However, a lubricating oil composition which meets the requirements for polishing rate and surface smoothness of an object to be polished while preventing charge by static electricity has not been studied much. As means of providing antistatic properties, there is a method in which a surfactant is added. However, as this causes the corrosion of the magnetic portion of the magnetic head, it is difficult to provide sufficiently high antistatic properties by adding a surfactant.
As a cleaner for removing a stain such as wax adhering to such an electronic part in its production process, there is known one which comprises a hydrocarbon solvent and an organic onium salt such as tetraoctylammonium.2,2,2-trifluoro-N-(trifluoromethanesulfonyl)acetamide (refer to JP-A 2004-285354). Although this cleaner has excellent antistatic properties and rarely causes the breakdown of a device during cleaning due to the function of the above organic onium salt, use of this cleaner in a lubricant for polishing the above magnetic head is utterly unknown.